1. Field of the Invention
The present invention pertains to a light emitting device and a manufacturing method for a light-emitting device (LED), and particularly to a highly efficient light-emitting structure and a manufacturing method for an LED. In particular, the light-emitting structure proposed herein is based on the Group-III GaN-based materials and has a resonant cavity structure used to enhance luminous efficiency of the generated light therefrom.
2. Descriptoin of Related Art
Light-emitting devices (LEDs) have been developed and on the market for years and are useful in providing lights as generally recognized. The use of LEDs in digital watches and calculators are well known. As we see, it may also find other important applications in communications and other areas, such as mobile phone and some appliances. Recently, there is a trend that LEDs be further applied to ordinary human living utilization, such as large panels, traffic lights and lighting facilities and the perspective thereof are looking good. Therefore, LEDs are increasingly playing an important role in our daily life and deserving more efforts. As is transparent to those skilled in the art, LEDs are produced based on some semiconductor materials and emits lights by dint of the behaviors aroused in the semiconductor materials in the presence of an applied electrical bias.
In particular, an LED gives off a light by a light-emitting structure therein generally composed of some Group-III (compound) semiconductor owing to its stronger inclination of recombination of electrons and holes. In principle, an LED is basically a well-known p-n junction structured device, i.e., a device having a p region, an n region and a transient region therebetween. With a forward voltage or current bias applied, the majority of carriers in the p or n regions drift respectively towards the other region (through the transient region) in the device due to the energy equilibrium principle and a current is accounted for, in addition to the general thermal effects. When electrons and holes jumped into a higher value of energy band with the aid of electrical and thermal energy, the electrons and the holes recombine there and give off lights when they randomly and spontaneously fall back to a reduced energy state owing to thermal equilibrium principle, i.e. spontaneous emission.
Afterwards, the concept and structure widely used in semiconductor device of the multi-quantum well (MQW) layers are introduced into an LED structure. Generally, the MQW layers are formed between the p and the n regions in the above-mentioned p-and-n structure, which forms the so-called “PIN” structure. With the aid of the MQW active layers, the possibility of recombination of the electrons and holes in the p-n junction based device are efficiently enhanced and the luminous efficiency thereof is upgraded considerably. Further, the color of a light emitted from the LED may be controlled through a choice of the materials, dopant concentration and layer thickness in the MQW layers.
However, the current LEDs are still not sufficient in brightness in serving as some light supplying facilities, and which has long been the common issue that all researchers in the field concern and desire to address.
In view of the foregoing problem, the inventors of the present invention provides a novel colored light emitting diode with a different structure so as to increase luminous efficiency of the currently used LED.